Stereoselectivity in complexation of primary alkylammonium cations by the diastereotopic faces of chiral asymmetric crowns

Abstract

The temperature-dependent ¹H n.m.r. spectra of the 1:1 complexes formed between crowns D-(1), DD-(2), D-(3), and DD-(4) and primary alkylammonium cations in solution are interpreted in terms of equilibria involving diastereoisomeric complexes of (i) similar strengths in the case of the galacto-crowns D-(1) and DD-(2) and (ii) dissimilar strengths in the case of the gluco-crowns D-(3) and DD-(4) where a secondary interaction of a dipole-induced dipole type appears to be responsible for the stereoselectivity.